As a petroleum refining apparatus is operated, heavy oil contents, which are generated when petroleum is partly polymerized upon heating, and soil components, such as the sludge produced upon deterioration (or degradation) of metals in the inner wall of the apparatus (hereinafter collectively referred to as “soil components”), adhere to the inside of heat exchangers, pipes, heating furnaces, desalters, and the like (hereinafter collectively referred to as “petroleum refining apparatus”) constituting the apparatus.
When such soil components accumulate within the petroleum refining apparatus, the petroleum refining efficiency may be reduced. To prevent this from happening, the inside of the petroleum refining apparatus is periodically washed. While water washing with a jet of water has generally been widely used, methods in which an aqueous surfactant solution or a petroleum solvent is circulated within the petroleum refining apparatus for washing have recently been proposed as a method for shortening the washing time.